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Carbonate hardness is a measure of the amount of calcium and magnesium present in water. As it turns out, these elements are vital to the health and well-being of certain fish – including trout, koi and goldfish – because of their ability to neutralize acids in water and stabilize healthy pH levels.

But why, you might logically ask, are acids a concern? You’ve just asked the sixty-four thousand dollar question. In the course of regular pond maintenance, it’s common to apply algaecides and herbicides. Often, those products contain chemicals that are acidic, and when they’re applied, they can cause pH fluctuations that certain fish are ill-equipped to handle. Thus, water that’s “hard” – or rich in calcium and magnesium – helps to minimize those fluctuations, protecting fish from harm. Other environmental factors, including runoff from fertilized lawns, can have a similar effect on pH, making it all the more important to ensure that your water maintains a safe level of carbonate hardness.

As a rule, algaecides and herbicides indicate a recommended level of carbonate hardness in pond water to ensure that their effects won’t harm fish. Low carbonate hardness is generally indicated when calcium and magnesium levels are below 50 parts per million (ppm). And fortunately, it’s easy to test your water to determine its carbonate hardness levels. With our Carbonate Hardness Test Strips, you can test your water prior to each application of algaecides and herbicides. If levels are above the range indicated on the product you’re planning to use, the pH of the water will be safe for fish even after application.